U.S. patent number 10,239,194 [Application Number 15/074,099] was granted by the patent office on 2019-03-26 for tensioning device for extending a threaded bolt.
The grantee listed for this patent is Frank Hohmann, Jorg Hohmann. Invention is credited to Frank Hohmann, Jorg Hohmann.
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United States Patent |
10,239,194 |
Hohmann , et al. |
March 26, 2019 |
Tensioning device for extending a threaded bolt
Abstract
A tensioning device for a thread end portion of a bolt has a
cylindrical housing and a piston, moveable in longitudinal
direction therein and connectable to a hydraulic supply. An
interchangeable sleeve extends centrally through the piston. At its
end it has an internal thread with engagement length to be screwed
onto the thread end portion. The sleeve has a radially expanded
portion carried axially by a carrier face of the piston. In order
to prevent the sleeve from prematurely contacting the threaded bolt
when mounting the bolt tensioning cylinder and prevent damage to
the threads, the sleeve is moveable longitudinally relative to the
piston. The longitudinal sleeve travel is defined by the carrier
face as first longitudinal stop and by a second longitudinal stop.
The longitudinal sleeve travel is at least equal to, preferably
greater, than the engagement length of the internal thread of the
sleeve.
Inventors: |
Hohmann; Frank (Warstein,
DE), Hohmann; Jorg (Meschede, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hohmann; Frank
Hohmann; Jorg |
Warstein
Meschede |
N/A
N/A |
DE
DE |
|
|
Family
ID: |
55646267 |
Appl.
No.: |
15/074,099 |
Filed: |
March 18, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160271775 A1 |
Sep 22, 2016 |
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Foreign Application Priority Data
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Mar 19, 2015 [DE] |
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10 2015 104 133 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B25B
29/02 (20130101); B23P 19/067 (20130101); F16B
31/043 (20130101) |
Current International
Class: |
B25B
29/02 (20060101); B23P 19/06 (20060101); F16B
31/04 (20060101) |
Field of
Search: |
;81/57.38 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 130 507 |
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Dec 1972 |
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DE |
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23 28 444 |
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Jan 1975 |
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DE |
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Primary Examiner: Thomas; David B.
Attorney, Agent or Firm: Huckett; Gudrun E.
Claims
What is claimed is:
1. A tensioning device for extending a thread end portion of a
threaded bolt, the tensioning device comprising: a cylindrical
housing configured to be supported against a fixed abutting base;
at least one piston disposed in the cylindrical housing and
comprising a carrier face, wherein the at least one piston is
moveable in a longitudinal direction of the at least one piston
within the cylindrical housing and is configured to be connected to
a hydraulic supply; an interchangeable sleeve extending centrally
through the at least one piston and comprising a first end having
an internal thread with an engagement length, the internal thread
configured to be screwed onto the thread end portion of the
threaded bolt; the interchangeable sleeve comprising a radially
expanded portion configured to be supported axially by the carrier
face of the at least one piston; the interchangeable sleeve
moveable longitudinally in relation to the at least one piston,
wherein a longitudinal travel of the interchangeable sleeve is
delimited by the carrier face forming a first longitudinal stop and
by a second longitudinal stop opposite the first longitudinal stop;
wherein a length of the longitudinal travel is at least equal to
the engagement length of the internal thread of the interchangeable
sleeve.
2. The tensioning device according to claim 1, wherein the length
of the longitudinal travel is greater than the engagement length of
the internal thread of the interchangeable sleeve.
3. The tensioning device according to claim 1, further comprising a
first spring acting on the interchangeable sleeve such that the
interchangeable sleeve is forced by the first spring against the
second longitudinal stop.
4. The tensioning device according to claim 3, further comprising a
second spring supported with a first end against the cylindrical
housing and supported with a second end against the at least one
piston, wherein the first spring is weaker than the second
spring.
5. The tensioning device according to claim 4, wherein the at least
one piston comprises a wall enclosing a cavity, wherein the
radially expanded portion of the interchangeable sleeve is arranged
in the cavity, wherein the cavity has a length such that the
radially expanded portion is moveable in the cavity across the
longitudinal travel, wherein the wall of the at least one piston
has an upper end face, wherein the second end of the second spring
is supported against the end face of the wall.
6. The tensioning device according to claim 5, wherein the wall
comprises a cylindrical outside surface and the cylindrical housing
comprises an inside wall, wherein the cylindrical outside surface
of the wall and the inside wall of the cylindrical housing together
form a longitudinal guide of the at least one piston.
7. The tensioning device according to claim 3, wherein the first
spring is a coil spring enclosing a longitudinal portion of the
interchangeable sleeve and comprising a first end supported against
the interchangeable sleeve.
8. The tensioning device according to claim 7, wherein the first
spring comprises a second end supported against a face of the
cylindrical housing.
9. The tensioning device according to claim 8, wherein the
interchangeable sleeve comprises a collar provided at an end of the
interchangeable sleeve remote from the internal thread, wherein the
first end of the first spring is supported against the collar.
10. The tensioning device according to claim 9, wherein the
interchangeable sleeve comprises an end piece and the collar is
formed on the end piece.
11. The tensioning device according to claim 10, wherein the end
piece is screw-connected to a main body of the interchangeable
sleeve.
12. The tensioning device according to claim 1, further comprising
a socket fixed to the cylindrical housing and enclosing an end
portion of the interchangeable sleeve, wherein the end portion is
remote from the internal thread, wherein the end portion comprises
a first marking and the socket comprises a second marking, wherein
the first and second markings are to be aligned with each
other.
13. The tensioning device according to claim 12, wherein the first
marking is a visual marking and the second marking on the socket is
a sighting window.
14. The tensioning device according to claim 13, wherein the first
marking is a color marking or a contrast marking.
15. The tensioning device according to claim 13, wherein the visual
marking is externally visible in the sighting window only when the
radially expanded portion of the interchangeable sleeve bears on
the carrier face.
Description
BACKGROUND OF THE INVENTION
The invention relates to a tensioning device for tensile stressing
(extending) a threaded bolt on its thread end portion, having a
cylindrical housing which is supported against a fixed abutting
base and has at least one piston, moveable in a longitudinal
direction therein and connectable to a hydraulic supply, and having
an interchangeable sleeve, which leads centrally through the
piston, at its end having an internal thread with an engagement
length that can be screwed onto the thread end portion, the sleeve
being provided with a radially expanded portion designed to be
carried axially by a carrier face formed on the piston.
U.S. Pat. No. 8,375,554 B2 discloses a hydraulically functioning
bolt tensioning device having these features. For stressing the
threaded bolt an interchangeable sleeve, which is provided at its
lower end with an internal thread for screwing to the threaded
bolt, is arranged in the cylindrical housing of the tensioning
device. The interchangeable sleeve can be carried axially by a
hydraulically actuated piston of the tensioning device, and for
this purpose is provided with a radially expanded flange or
collar.
Bolt tensioning devices having multiple interchangeable sleeves are
also disclosed by U.S. Pat. No. 8,616,094 B2, for example. Here the
inner interchangeable sleeve is displaceable in an axial direction
relative to the outer interchangeable sleeve and is pre-sprung
against the outer interchangeable sleeve. After screwing on the
interchangeable sleeves the bolt is axially tensioned by two
hydraulically operated pistons, which move the outer and the inner
interchangeable sleeves simultaneously in an axial direction. The
total pre-tensioning force is transmitted to two separate threads
of the bolt by a thread of the inner interchangeable sleeve and
thread of the outer interchangeable sleeve.
In the case of a bolt tensioning device disclosed by US
2011/0271798 A1 also, the threaded bolt is axially stressed by
means of an interchangeable sleeve engaging in the thread of the
threaded bolt. This sleeve can be carried axially by pistons of the
tensioning device arranged in series, in that the interchangeable
sleeve is provided close to its upper end with a thread, onto which
a flange or collar, undercut by the uppermost piston, is screwed. A
spring arrangement arranged around the interchangeable sleeve is
supported against the collar and in addition against the
interchangeable sleeve so that the latter always bears against the
uppermost piston. In order to screw the interchangeable sleeve onto
the threaded bolt, the tensioning device is mounted onto the
threaded bolt from above and rotated about its axis so that the
interchangeable sleeve is screwed onto the free threaded portion of
the threaded bolt.
Screwing the tensioning device on in this way and rotating it about
its axis is time-consuming and in view of the weight of such bolt
tensioning devices also laborious. Moreover, mounting the heavy
tensioning device leads to a sometimes hard, uncontrolled collision
between the threaded portion of the interchangeable sleeve and the
threaded bolt, which may cause damage to the threads involved.
It is the object of the invention, through design measures on the
tensioning device, to avoid the interchangeable sleeve coming into
premature contact with the threaded bolt whilst mounting the bolt
tensioning cylinder, and in this way to prevent damage to the
threads involved.
SUMMARY OF THE INVENTION
For this purpose, a tensioning device of the aforementioned kind is
characterized in that the interchangeable sleeve is moveable
longitudinally in relation to the piston, the longitudinal travel
of the interchangeable sleeve being delimited by the carrier face
as a first longitudinal stop and by a second longitudinal stop
opposite the first longitudinal stop, and a length of the
longitudinal travel being at least equal to, and preferably greater
than, the engagement length of the internal thread of the
interchangeable sleeve.
With a tensioning device configured in this way, premature contact
between the thread on the interchangeable sleeve and the thread on
the threaded bolt cannot occur when mounting the tensioning device
so that unwanted damage to the threads involved is avoided in this
fitting situation.
According to one embodiment of the tensioning device, the
interchangeable sleeve is supported under the force of a spring
against the second longitudinal stop. The spring causes the
interchangeable sleeve to automatically assume a basic position
inside the bolt tensioning device in which it is retracted so far
upwards that, when mounting the bolt tensioning cylinder onto the
threaded bolt, no contact yet occurs between the interchangeable
sleeve and the thread end of the threaded bolt. Only against the
force of the spring is it possible to move the interchangeable
sleeve towards the threaded bolt; only then the interchangeable
sleeve can be screwed onto the thread end portion of the threaded
bolt through engagement of the threads involved.
According to a further embodiment, the spring holding back the
interchangeable sleeve is a coil spring, which encloses a
longitudinal portion of the interchangeable sleeve and is supported
by its first end against the interchangeable sleeve. The spring is
preferably supported by its second end against a face on the
cylindrical housing. In addition, the first end of the spring is
preferably supported against a collar, with which the
interchangeable sleeve is provided at its end remote from the
internal thread. This collar may be formed on an end piece, which
is fixed to the interchangeable sleeve preferably by a screw
connection.
According to a further embodiment, the piston of the tensioning
device, for receiving the radially expanded portion of the
interchangeable sleeve, is provided with a cavity of a length such
that the expanded longitudinal portion is moveable therein over the
longitudinal travel of the interchangeable sleeve. In this case the
cavity is enclosed by a wall of the piston which comprises an upper
end face, a spring being supported against this end face with one
end and against the cylindrical housing with the other end. The
outside surface of the wall is preferably cylindrical and forms
together with the inside wall of the cylindrical housing a
longitudinal guide of the piston.
A further embodiment is characterized by a socket which is fixed to
the cylindrical housing and which encloses an end portion of the
interchangeable sleeve remote from the internal thread, the end
portion and the socket each being provided with markings to be
aligned or matched with each other. The marking on the
interchangeable sleeve is preferably a visual marking, for example
a color marking or a contrast marking, and the marking on the
socket is preferably a sighting window in the socket. In this
embodiment, the visual marking is visible from the exterior in the
sighting window only when the interchangeable sleeve bears on the
carrier face, and the tensioning can therefore commence.
BRIEF DESCRIPTION OF THE DRAWINGS
Further details and advantages emerge from the following
description of an exemplary embodiment represented in the drawing,
in which:
FIG. 1 shows a simplified, sectional representation of a
hydraulically functioning threaded bolt-tensioning device, applied
in alignment with a threaded bolt and supported on a base.
FIG. 2 shows the same threaded bolt-tensioning device in the
further course of a fitting situation.
FIG. 3 shows the same threaded bolt-tensioning device during the
tensioning process.
DESCRIPTION OF PREFERRED EMBODIMENTS
The hydraulically operated tensioning device described here serves
for tightening, primarily retightening, and possibly also
slackening highly stressed bolted connections. The tensioning
device is used to apply a predefined pre-tensioning force F (FIG.
3) to a threaded bolt 3 in the longitudinal direction of the bolt
for a certain length of time in order to meanwhile tighten or
retighten a nut 4 of the bolted connection screwed onto the
threaded bolt 3.
An interchangeable sleeve 10 arranged centrally in the tensioning
device is provided at its one end with a sleeve portion having an
internal thread 11. Before commencing the tensioning process, the
internal thread 11 is screwed onto a thread end portion 3A of the
threaded bolt 3 projecting beyond the nut 4. Then the
interchangeable sleeve 10 thus screwed onto the threaded bolt 3 is
hydraulically tensioned by applying the force F, thereby stressing
and axially tightening the threaded bolt 3 in the longitudinal
direction. The underside of the nut 4 thereby lifts off so that the
nut 4 can be turned with virtually no resistance and tightened in
this way.
The hydraulic tensioning mechanism is enclosed by a
pressure-resistant cylindrical housing 1. This may be of a modular
assembly comprising a plurality of cylindrical portions. The rigid,
downward continuation of the cylindrical housing 1 forms a support
tube 2 enclosing the nut. The support tube 2 may be integrally
formed with the cylindrical housing 1, or alternatively it may be a
separate component from the cylindrical housing 1, for example one
that can be attached thereto. The support tube 2 is open on its
underside and is supported on a fixed base 8, which serves as
abutment in the tensioning process. In the exemplary embodiment
described herein, the base 8 is the machine part on which the nut 4
is also supported by its underside. In addition, there may also be
a mechanism, which serves for turning the nut 4, functioning
through an opening 9 in the support tube 2. This turning is
naturally possible only when the tensioning device is working, that
is to say stressing or extending the bolt, and the nut 4 is
therefore not subject to considerable friction.
On the side of the cylindrical housing 1 is a hydraulic connection
7, via which the hydraulic working chamber of the tensioning device
has a valve-controlled connection to an external hydraulic
supply.
The cylindrical housing 1 comprises one or alternatively more
hydraulic cylinders, which are connected to the external hydraulic
supply via the hydraulic connection 7 and a flexible,
pressure-resistant hydraulic line. A longitudinally moveable piston
15 is arranged in each hydraulic cylinder, sealed off towards the
inside wall of the cylinder. In the exemplary embodiment described
herein, there is only one cylinder stage and therefore also only
one piston 15.
The piston 15 is raised by feeding hydraulic pressure into the
hydraulic working chamber 18 of the cylinder. This occurs in
opposition to the pressure from a strong spring 17 acting on the
piston 15 from above. The spring 17 here comprises annular disk
springs stacked one on top of another and therefore connected in
series. The spring 17 serves as piston return spring and acts
directly on the piston 15 with a force which strives to keep the
piston 15 in the basic position reproduced in FIG. 1 and in FIG. 2,
in which the hydraulic working chamber 18 is smallest.
The piston 15 annularly surrounds the interchangeable sleeve 10. It
is provided on its inside edge with a circumferential step, which
remote from the base 8 forms a carrier face 21, on which the
interchangeable sleeve 10 is supported by way of a radially
expanded portion 25 affixed thereto. In this way the
interchangeable sleeve 10 can be axially carried by the piston
15.
The interchangeable sleeve is of three-part construction and is
composed of a narrow main body 24, a flange forming the radially
expanded portion 25, and an end piece 26.
The main body 24 of the interchangeable sleeve is situated
centrally on the longitudinal axis of the tensioning device, and is
provided at its bolt-side end with the internal thread 11 for
screwing onto the threaded bolt 3. The flange forming the radially
expanded portion 25 is screwed onto the main body 24, inasmuch
producing a rigid unit. The end piece 26 is situated at the other
end of the interchangeable sleeve 10, that is to say the end remote
from the thread 11. The end piece 26 is also screwed to the main
body 24 and therefore forms a rigid unit with the latter.
At its upper end the interchangeable sleeve 10 is provided with a
polyhedron 28, to which a standard commercial tool can be applied
in order firstly to turn the interchangeable sleeve 10 in relation
to the cylindrical housing 1 and secondly in order to move the
interchangeable sleeve 10 in a longitudinal direction towards the
threaded bolt 3. In the exemplary embodiment described herein, this
movement is performed in opposition to the force of a spring 30,
which is supported by its first end against the interchangeable
sleeve 10, and by its second end against the cylindrical housing 1.
The spring 30 ensures that the interchangeable sleeve 10 normally
assumes a position in which it is supported on the second
longitudinal stop 22.
The function of the second longitudinal stop 22 here is assumed by
the underside of the strong spring 17, which acts upon the piston
15. This spring 17 is significantly stronger or stiffer than the
spring 30 bearing against the interchangeable sleeve.
The spring 30 takes the form of a coil spring, which encloses a
narrow longitudinal portion of the interchangeable sleeve 10. The
spring 30 is supported on the interchangeable sleeve, not directly
on the main body 24 of the interchangeable sleeve but on the end
piece 26 forming a collar of the interchangeable sleeve.
The piston 15 is provided with a wall 42, which encloses a cavity
and extends in a longitudinal direction up to an end face 43,
against which the spring 17 is supported by its lower end. With its
other end the spring 17 is supported from inside against a face of
the cylindrical housing 1. The outside of the wall 42 is
cylindrical and together with the inside wall of the cylindrical
housing 1 forms a part of the longitudinal guide of the piston
15.
In order to avoid a hard impact of the thread 11 of the
interchangeable sleeve 10 on the external threads of the threaded
bolt 3 when mounting the bolt tensioning cylinder onto the threaded
connection, as is reproduced in FIG. 1, and thus prevent damage to
the threads, the maximum longitudinal travel L2 over which the
portion 25 of the interchangeable sleeve is able to move in a
longitudinal direction between its bearing contact against the
first longitudinal stop 21 and its bearing contact against the
longitudinal stop 22 is at least equal to the engagement length L1
of the internal thread 11, and preferably somewhat greater than
this engagement length. The term engagement length L1 here denotes
that length over which the thread 11 is in engagement with the
threaded bolt 3 when the interchangeable sleeve 10 is fully screwed
onto the thread end portion 3A.
Arranging the interchangeable sleeve 10 so that it is
longitudinally moveable relative to the piston 15 allows the
interchangeable sleeve 10 to assume a basic position inside the
tensioning device in which it does not bear on the piston 15, but
rather with its portion 25 bears against the second longitudinal
stop 22. This ensures that during mounting of the tensioning device
no contact can yet occur between the thread 11 of the
interchangeable sleeve and the threads of the thread end portion 3A
so that in this fitting situation, reproduced in FIG. 1, the
possibility of damage is excluded. Rather than extending to the
outermost end of the interchangeable sleeve 10, there is nothing to
prevent the internal thread 11 there actually being replaced by a
short, threadless collar 35, which in the situation according to
FIG. 1 overlaps the threaded bolt 3 somewhat in a longitudinal
direction. The collar 35 serves for simplified initial centering of
the tensioning device on the threaded bolt 3. Since it lacks a
threaded structure, however, it is not likely to damage the
external thread of the threaded bolt 3.
Once the tensioning device is settled on the base 8 in alignment
with the threaded bolt 3 according to FIG. 1, in the next step,
which is reproduced in FIG. 2, the interchangeable sleeve 10 is
screwed onto the thread end portion 3A. For this purpose, an
appropriate tool, for example a bolt tool, is applied to the flat
face 28 and used to move the interchangeable sleeve 10 initially
towards the threaded bolt 3 until the internal thread 11 engages in
the external thread of the bolt 3. Further turning of the tool then
leads to a screwing action, in which the portion 25 of the
interchangeable sleeve 10 inside the cavity of the piston 15 covers
the longitudinal travel L2, until finally the portion 25 encounters
the first longitudinal stop 21. In this situation, which is
reproduced in FIG. 2, the internal thread 11 engages over its full
engagement length L1 in the external thread of the bolt 3.
In this situation according to FIG. 2 a marking 37 located on the
end piece 26 is precisely on a level with a sighting window 38,
which is situated in a socket 40. The socket 40 is fixed to the
cylindrical housing 1 and encloses the end portion of the
interchangeable sleeve 10 remote from the internal thread 11. The
marking 37 present on sides of the interchangeable sleeve is here a
colour or contrast marking arranged in a circumferential groove of
the end piece 26. The groove itself is also suitable as a marking
37, provided that it is sufficiently discernible through the
sighting window 38 of the socket 40 forming the countermark. If, in
accordance with FIG. 2, the two markings 37, 38 lie one behind
another on the same level, this indicates to the operator of the
appliance that the interchangeable sleeve 10 is screwed fully, that
is to say over its entire thread engagement length L1, to the
thread end portion 3A of the threaded bolts, and the tensioning
process can begin.
This tensioning process is reproduced in FIG. 3. Under the
hydraulic pressure in the working chamber 18 the piston 15 is
raised, carrying the interchangeable sleeve supported on the
carrier face 21 with it. The threaded bolt 3 is stressed and
tightened and a gap is formed between the underside of the net 4
and the base 8. The nut 4 can then be retightened by effortless
turning, preferably through the openings 9.
Second markings 47, 48, which are situated below or above the
markings 37, 38 already described, serve for monitoring the
tensioning process. When the annular marking 47 on the
interchangeable sleeve is situated at the same levels as the
sighting window 48 in the socket 40 serving as countermark, it is
apparent from this correlation--and the machine operator is advised
accordingly--that the maximal admissible tensioning travel has been
reached.
The specification incorporates by reference the entire disclosure
of German priority document 10 2015 104 133.2 having a filing date
of Mar. 19, 2015.
While specific embodiments of the invention have been shown and
described in detail to illustrate the inventive principles, it will
be understood that the invention may be embodied otherwise without
departing from such principles.
LIST OF REFERENCE NUMERALS
1 cylindrical housing 2 support tube 3 threaded bolt 3A thread end
portion 4 nut 7 hydraulic connection 8 base 9 opening 10
interchangeable sleeve 11 internal thread 15 piston 17 spring 18
hydraulic working chamber 21 carrier face, first longitudinal stop
22 second longitudinal stop 24 main body 25 radially expanded
portion 26 end piece 28 polyhedron, flat face 30 spring 35 collar
37 marking 38 marking 40 socket 42 wall 43 end face 47 marking 48
marking F pre-tensioning force L1 thread engagement length L2
longitudinal travel
* * * * *